MODELING DIFFUSION AND REACTION IN SOILS: III. PREDICTING GAS DIFFUSIVITY FROM THE CAMPBELL SOIL-WATER RETENTION MODEL :

A method has been proposed for deriving a characteristic determining flow in porous systems. This characteristic combines both area and path-length factors used by earlier authors. For a gas, diffusive flow is proportional to the 4/3 power of the gas-filled porosity, and this function has been derived from consideration of the planar distribution of spherical pores and the interaction of two adjacent planes.